cardiovascular system 2

What 2 vessels transport oxygenated blood

• arteries

• arterioles

What vessels transport deoxygenated blood

• venules

• veins

What vessel is involved in gas exchange

• capillaries

What are the 3 layers in the artery and vein

• tunica interna / intima

  • innermost layer (endothelium)

  • tunica media

    • middle layer

  • tunica externa / adventitia

    • outermost layer

What is a single capillary layer called

endothelium

What is the structure of tunica interna /intima

• simple squamous epithelium

  • allows smooth blood flow

• continuous inner lining throughout CV system

What is the structure of tunica media

• circular, smooth muscle

• elastic fibre → change diameter

• connective tissue

• thicker in arteries than veins

• vaso constriction & dilation

• innervated by small vascular nerves

  • sympathetic

What is the structure of tunica externa

• sheath of connective tissue

  • elastic

  • fibrous

• thickest tunic in vein

• blend with surrounding connective tissue

What is the function of large elastic arteries

• blood conduction

  • conducting arteries

• absorb pressure changes during cardiac cycle

What is the function of elastic fibres

• create elastic recoil

  • propel blood onwards when ventricles relax

What is the function of the windkessel effect

• steadies blood pressure

What is the function of muscular arteries

• distribution of blood

  • to skeletal muscle + organs

• capable of greater vasoconstriction and vasodilation

  • adjust rate of blood flow

What is the function of arterioles

• deliver blood to arteries

  • resistance vessels

• small arteries slow blood flow

• regulate blood pressure

What is the function of precapillary sphincters

• cuff of muscle that controls blood flow into capillary bed

  • close and blood flows out of bed

    • throughfare channel

What is the structure and function of capillaries

• single layer of simple squamous epithelium & basement membrane

• slow flow

  • aids exchange of nutrients & wastes between blood and tissue fluid

What are the 3 types of capillaries which differ according to leakiness

• continuous

• fenesrated

• sinusoid

What are continuous capillaries

• continuous lining

• permeable to small molecules

  • water, ions, glucose

• skeletal muscles & lungs

What are fenestrated capillaries

• has pores covered with diaphragm

• permeable to larger molecules

  • nutrients

• kindey & small intestine

What are sinusoid capillaries

large open pores

• permeable to largest molecules

  • plasma proteins, cells

What are the 3 features of veins

• thinner walls than arteries with the same diameter

• adapt to variations in volume and pressure

  • expandable

• contain valves

  • thin folds of tunica interna that prevent backflow

What is the distribution of blood

• 60% of blood volume at rest is in systemic veins

  • function as blood reservoir

• capacitance vessels

  • blood diverted form veins in skin and organs

What is capillary exchange

• movement of materials in and out of capillary

• aided by millions of capillaries and slow flow

What is simple diffusion of plasma

• plasma solutes pass freely across lipid bilayer or through fenestrations or intercellular clefts

• down concentration gradient

What is transcytosis

• tiny vesicles cross endothelium by endocytosis & exocytosis

  • carry small amounts of molecules that can’t pass membrane

• insulin & maternal antibodies

Why is bulk flow important

• regulation of blood volume & interstitial fluid

What is hydrostatic pressure

• mechanical pressure exterted on a membrane by a fluid

• fluid pushes on walls

What is osmotic pressure

• osmotic pressure exerted on a membrane by particles in a fluid

• particles pulls on walls

What is filtration from blood into interstitial fluid

• blood hydrostatic pressure pushes fluid out of capillary

What is reabsorption from interstitial fluid into blood

• blood colloid osmotic pressure pulls fluid back into capillary

What is net filtration pressure and what does it determine

• pressure in capillary compared to interstitial fluid

• determines whether fluids enter or leave capillary

What is the effect of positive pressure at arterial

• promotes filtration